The invention relates to a process for preparing a water-continuous dairy product and to a product obtainable by the process.
Water continuous dairy products such as quark and other fresh cheeses, cream, creme fraiche, etc. can be used for many different applications. They can for example be spread on bread, on top of or instead of e.g. butter or margarine, they can be eaten as dessert or they can be used as ingredient in the preparation of other foods. However when using such dairy products in cooking, e.g. when incorporating them in hot or sour food preparations, often the dairy product proves to be unstable, i.e. it separates, thereby imparting an unpleasant appearance and mouthfeel to the food preparation. Creme fraiche is often used for cooking because it is relatively stable and the risk of such separation occurring is fairly small. However, the fat content of creme fraiche is rather high, typically about 35% or more. When we evaluated a reduced fat creme fraiche product having a fat content of 17%, we found it was not stable in cooking but it often separated when including it e.g. in sour sauces or hot dishes.
We have now found a way to overcome this problem. Accordingly the invention provides a process for preparing a water continuous dairy product suitable for use in cooking, comprising the steps of
A acidifying a cream having a fat content of at least 25% and a non-fat milk solids content of at least 6.5% to cause the pH of the cream to become 4.0-5.2, preferably 4.0-4.9, more preferably 4.1-4.6
B preparing a mixture comprising 30-70% of the acidified cream and 30-70% of fresh acid-coagulated curd having a pH of 4.2-5.2, preferably 4.2-4.9, more preferably 4.4-4.7
C optionally, homogenising the mixture such that the product has a dry matter content of 25-40%, a fat content of 13-27%, a protein content of at least 4.5% and a pH of 4.2-5.2, preferably 4.2-4.9, more preferably of 4.4-4.8.
Preferred embodiments of the process are given in claims 2-9.
The invention also provides a water continuous dairy product suitable for use in cooking, obtainable by the present process, having a dry matter content of 25-40%, a fat content of 13-27%, a protein content of at least 4.5% and a pH of 4.2-5.2, preferably 4.2-4.9, more preferably 4.4-4.8, that is stable when incorporated in a hot or sour food preparation. Preferred embodiments of the product are given in claims 11-13.
Deutsche Molkerei Zeitung vol. 109 no. 18 page 538-543 describes the influence of protein additives on the structure of fresh cheese.
U.S. Pat. No. 3,929,892 describes the production of a cream cheese type product from dairy ingredients including cottage curd.
Food product development vol 9. no.9 1975 pages 68-74 describes the development of cheese flavoured dairy spreads.
None of these documents describe the particular process steps as outlined above nor products which can be obtained through such a process.
The present product is not only suitable for cooking. It can also be spread on bread, used for cold dipping e.g. with snacks, eaten as dessert, if so desired e.g. in combination with fresh or preserved fruits, used in bakery products, e.g. as a layer in or on top of cakes, etc. The product has a pleasant taste, e.g. not very different from creme fraiche, but with an extra, fresh touch. It typically has a nice smooth texture. Although the product will usually not be airated, it can have a consistency resembling that of firm, whipped cream. We found the product particularly attractive for use in a wide variety of warm and cold cooking, for example in making sauces, soups and casseroles. We found that the product can be stable even under demanding circumstances, e.g. when used in soups that still need some boiling or when used in tomato/vinegar based dressings having a very low pH. Under such conditions we found the reduced fat creme fraiche was not stable, it separated.
The cream employed in step A of the process has a non-fat milk solids content of at least 6.5%. This is higher than is commonly present in dairy cream. Usually regular dairy cream from cow""s milk, prepared e.g. by separating whole milk into cream and skimmilk, which may be standardized e.g. by recombining cream with some skimmilk to obtain a fat content of e.g. 40%, optionally in combination with homogenisation, contains about 5% non-fat milk solids. Preferably the present cream is derived from cow""s milk, but its non-fat milk solids content is raised. This is preferably done by combining 95-99% of a dairy cream having a usual non-fat milk solids content, with 1-5% milk solids, preferably skimmilk powder, and subjecting the mixture obtained to homogenisation. Before homogenisation, the mixture can be left to stand for some time, e.g. with gentle stirring to allow the milk solids to dissolve. By dairy cream is meant cream obtained by separating fat containing milk, preferably cow""s milk, into a high fat portion, cream, and a low fat portion, usually skimmilk. The cream may be standardized, e.g. by mixing back in some skimmilk, and/or homogenized. Such dairy cream typically has a non-fat milk solids content lower than the non-fat milk solids content of the milk from which it is prepared. In the present process, preferably skimmilk powder is dispersed in dairy cream to obtain the desired non-fat milk solids content, and the resulting mixture is homogenised. Homogenisation can be done using a homogenizer as commonly used in the dairy industry, e.g. using a single or multi-stage homogenizer operating at a pressure of 30-400 bar. The mixture may be pasteurised, e.g. at 70xc2x0 C. before or after the homogenisation. The resulting cream should have a fat contents of at least 25%, preferably it is 30-50%, especially 35-45%. The cream used in step A of the process preferably has a non-fat milk solids content of 7-12%, especially 7-9%.
To raise the milk solids content of the dairy cream, as an alternative to skimmilk powder for example sweet and/or sour buttermilk powder can be used, but preferably skimmilk powder is used.
Alternatively, the cream of step A of the process may consist of or comprise artificial cream, by which is meant cream in which part or all of the fat consists of vegetable oil or fat. Such artificial creams are well known in the art. Preferably, however, the cream in step A of the process is cream derived from milk of mammals, more preferably milk of ruminants, in particular cows"" milk.
It is essential for the pH of both the acidified cream and the curd, and also that of the end product to be low enough for coagulation of caseins, i.e. 5.2 or lower. On the other hand, to obtain optimal taste and texture properties, the pH should not be too low. We found that the pH of the acidified cream may be as low as 4.0 but should not be lower, while the pH of the curd and of the endproduct should not be below 4.2.
The cream in step A of the process may be acidified chemically, e.g. using lactic acid. Glucono delta lactone can also be used. Preferably however the cream is acidified with a lactic acid culture.
The lactic acid culture, i.e. a culture of bacteria capable of converting lactose into lactic acid, is added to the cream and the cream is kept at a suitable temperature to allow the fermentation to proceed and the pH to reduce. Preferably, the culture used is a yoghurt culture, e.g. a thermophilic culture comprising e.g. L. bulgaricus and S. thermophilus. As used herein the expression yoghurt culture includes yoghurt comprising live lactic acid bacteria. The culture is suitably added in an amount of 0.5-4%, preferably 1-3%, calculated on the weight of the cream. When using a common yoghurt culture, suitably the incubation temperature is about 45xc2x0 C., and the desired pH of 4.0-5.2, preferably 4.0-4.9, more preferably 4.1-4.6 will be reached in 4-5 hours. The fermentation can then be stopped by raising the temperature e.g. to 58-60xc2x0 C. for 5 minutes.
In step B of the process, a mixture is prepared comprising 30-70% of the acidified cream and 30-70% of a fresh acid-coagulated curd having a pH of 4.2-5.2, preferably, 4.2-4.9, more preferably 4.4-4.7. By an acid-coagulated curd is meant a curd in which the caseins have been caused to coagulate primarily by the action of acid. In the curd preparation a small amount of rennet may be employed to improve the texture of the curd or to facilitate its preparation. The indication fresh means that the curd has not been matured, as is commonly done with renneted curds e.g. for making matured cheeses like Gouda or Camembert. How to make fresh acid-coagulated curds is well known in the art. A suitable description is given e.g. by Guinee in 2nd Cheese Symposium, Nov. 22nd and 23rd 1990, National Dairy Products Centre, Moorepark, Fermoy, 31-43. The curd preferably is a low fat curd having a fat content of less than 5%, especially 0-3%. Particularly good results are obtained with the use of quark, especially low fat quark as the fresh acid-coagulated curd. The expression quark includes quark-equivalents by which are meant products that may not meet the legal definition of quark, e.g. because of the way they are prepared or their precise composition, but that are functionally and sensorically not essentially different from quark. Preferably, however, regular dairy quark is used, e.g. as described by Guinee cited above, or by J. G. Davis in Cheese, volumes I and III, Churchill Livingstone, London, 1965 and 1976. The curd preferably has a dry matter content of 14-32%, more preferably of 15-22%. The protein content of the curd preferably is 10-20%, especially 12-18%. In step B of the process e.g. some water and/or skimmilk can be included in the mixture to adapt the mixture composition to the composition desired for the end product. Preferably however the composition of the cream and of the curd and their mixing ratio are chosen such that such inclusion of e.g. water in step B of the process is not necessary. Preferably in step B 45-60% of the acidified cream is combined with 40-55% of the fresh acid-coagulated curd to obtain the mixture.
The mixture in step B can be prepared e.g. by mixing the composition in a tank with a mixing device, e.g. a ribbon mixer. Preferably, subsequent to step B the product is kept at a temperature for a period of time sufficient to at least pasteurize it. The product from step B, preferably after pasteurisation, can then be packed. The product so prepared, may show syneresis. Syneresis is different from the separation during cooking described above. Syneresis is the release of aqueous fluid from the main body of the water coutinuous dairy product in its pack. Contrary to the separation during cooking, syneresis does not adversely affect the quality of food preparations made with the dairy product.
However, especially non-professional customers may not like syneresis. To reduce this phenomenon it is therefore prefered to subject the mixture to homogenisation. Such homogenisation also contributes to the smoothness of the product.
The homogenisation is preferably done, applying a pressure of 30-400 bar, more preferably 40-150 bar. Preferably the homogenisation is done at an elevated temperature, e.g. of at least 60xc2x0 C. Preferably before and/or after the homogenisation in step C, the product is kept at a temperature for a period of time sufficient to at least pasteurize it. For example the mixture of step B can suitably be heated to 65-80xc2x0 C., preferably 70-75xc2x0 C. and homogenized at that temperature while the total holding time at that temperature before and after homogenisation can e.g. be 10 minutes to 4 hours. The product can then be cooled down and packed but preferably the product is packed while still hot. The packed product is then cooled down, preferably before the primary packs are combined in secondary packs such as outers to allow the cooling to proceed quickly. Good results are obtained by e.g. passing the primary packs through a cooling tunnel to reduce the temperature to below about 45xc2x0 C., preferably below about 35xc2x0 C. The cooled down product can then be packed in secondary packaging e.g. outers or shrink-wrapped trays. The secondary packs can be palletized and stored e.g. at 5-10xc2x0 C., before shipment.
Small amounts of other ingredients may be incorporated in the product, e.g. salt, flavour, spices or other taste and flavour imparting substances, preservative etc. Such ingredients can suitably be incorporated e.g. in or subsequent to step B of the process. Preferably however such ingredients are incorporated before homogenisation and pasteurisation of the product. If it is desired to include discrete particles in the product, e.g. herbs, pieces of nuts or fruit and the like, such particles are best incorporated after the homogenisation. Then preferably the holding time at elevated temperature is chosen such that these added particles are also pasteurised. Alternatively, such particles can be pasteurised separately before inclusion in the product.
Stabilizers such as gelatin, carrageenan, pectin, guargum etc, may also be incorporated in the product. Such stabilizers can reduce or prevent syneresis. They can be used if no homogenisation is applied but they may also be employed in combination with homogenisation. The amount of stabilizer preferably does not exceed 3%. Typically an amount of 0.1-2% will be adequate, an amount of 1% or less being especially preferred. However the use of such stabilizers is not necessary and very good product can be obtained without using such stabilizers.
Preferably the process is carried out such that the resulting dairy product has the following compositional properties:
Except for the contents of deliberately added materials such as pieces of nuts or fruit, the protein and fat contained in the product preferably originate from dairy milk. To prevent the product from getting an undesirable taste, the lactose content of the product should preferably not exceed 7%, more preferably it is kept below about 6%. The texture of the product is preferably smooth, the particle size as measured with a microscrew preferably being less than 50 xcexcm, more preferably less than 40 xcexcm, especially less than about 30 xcexcm. If larger particle sizes are obtained, this can normally be corrected by using a smoother curd as starting material, acidifying the cream to a slightly less low pH or renewing the culture used and/or by adapting the homogenisation step. The firmness of the product can suitably be characterised with a Stevens Texture Analyzer(copyright), operated with a 12.7 mm xcfx86 rod, speed 2 mm/s, penetration depth 10 mm. Before measuring, the sample is conditioned 24 hours at the measuring temperature. Preferably, the Stevens value at 10xc2x0 C. of the product is at least 100 g, more preferably 130-300 g, especially 150-250 g. Throughout this specification all parts, percentages and proportions are expressed by weight.